1. Field of the Invention
The herpesviruses include the herpes simplex viruses, comprising two closely related variants designated types 1 (HSV-1) and 2 (HSV-2). HSV-1 and HSV-2 are responsible for a variety of human diseases, such as skin infections, genital herpes, viral encephalitis, and the like.
The herpes simplex virus is a double stranded DNA virus having a genome of about 150 to 160 kbp packaged within an icosahedral nucleocapsid enveloped in a membrane. The membrane includes a number of virus-specific glycoproteins, the most abundant of which are gB, gC, gD and gE, where gB and gD are cross-reactive between types 1 and 2.
It is a matter of great medical and scientific interest to provide safe and effective vaccines against both HSV-1 and HSV-2. One promising approach has been the use of isolated glycoproteins which have been shown to provide protection when injected into mice subsequently challenged with live virus. One limitation on the use of such "subunit" vaccines, however, has been the difficulty in obtaining sufficient amounts of the glycoproteins. Heretofore, such glycoproteins have been obtained primarily from membranes isolated from a viral culture. The problems associated with large scale culturing of these pathogens and the difficulty in isolating the glycoproteins from the viral genome have substantially precluded the use of glycoprotein vaccines.
It would therefore be desirable to provide a safe and efficient method for the large-scale production of herpes simplex glycoproteins suitable for use as vaccines. In particular, it would be desirable to provide for the production of a polypeptide having an amino acid sequence similar to glycoprotein D, or a portion thereof, which polypeptide can elicit an immune response against both HSV-1 and HSV-2.
2. Description of the Prior Art
Subunit vaccines extracted from chick embryo cells infected with HSV-1 or HSV-2 are described in U.S. Pat. Nos. 4,317,811 and 4,374,127. See also, Hilfenhaus et al. (1982) Develop. Biol. Standard 52: 321-331, where the preparation of a subunit vaccine from a particular HSV-1 strain (BW3) is described. Roizman et al. (1982) Develop. Biol. Standard 52: 287-304, describe the preparation of non-virulent HSV-1.times.HSV-2 recombinants and deletion mutants which are shown to be effective in immunizing mice. Watson et al. (1982) Science 218: 381-384 describe the cloning and low level expression of the HSV-1 gD gene in E. coli, as well as expression of a cloned fragment by injection into the nuclei of frog oocytes. They also present the nucleotide sequence for the gD gene. Weis et al. (1983) Nature 302: 72-74 report higher level expression of gD in E. coli. This polypeptide elicits neutralizing antibodies in rabbits. Berman et al. (1983) Science 222: 524- 527 report the expression of glycoprotein D in mammalian cell culture. Lasky et al., Biotechnology, June 1984, pp. 527-532 report the use of this glycoprotein D for the immunization of mice. Cohen et al. (1984) J. Virol. 49: 120-108 reports the localization and chemical synthesis of a particular antigenic determinant of gD, contained within residues 8-23 of the mature protein.